Synchronization of databases with date range

ABSTRACT

A method of synchronizing at least a first and a second database each containing dated records such as events, wherein the records of the first and second databases are synchronized across a narrow date range narrower than the date range of the records of at least one of the databases. A prior synchronization can be performed across a prior date range. The date range of the prior synchronization is stored, along with the history file containing information representative of the content of the databases following the prior synchronization. When a current synchronization is performed, it is performed across a date range that combines the prior date range with the current date range.

An appendix forms part of this application. The appendix, which includes a source code listing relating to an embodiment of the invention, includes 691 frames on 8 microfiche.

This patent document (including the microfiche appendix) contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document as it appears in the Patent and Trademark Office file or records, but otherwise reserves all copyright rights whatsoever.

BACKGROUND OF THE INVENTION

This invention relates to synchronizing incompatible databases.

Databases are collections of data entries which are organized, stored, and manipulated in a manner specified by applications known as database managers (hereinafter also referred to as "Applications"). The manner in which database entries are organized in a database is known as the data structure. There are generally two types of database managers. First are general purpose database managers in which the user determines (usually at the outset, but subject to future revisions) what the data structure is. These Applications often have their own programming language and provide great flexibility to the user. Second are special purpose database managers that are specifically designed to create and manage a database having a preset data structure. Examples of these special purpose database managers are various scheduling, diary, and contact manager Applications for desktop and handheld computers. Database managers organize the information in a database into records, with each record made up of fields. Fields and records of a database may have many different characteristics depending on the database manager's purpose and utility.

Databases can be said to be incompatible with one another when the data structure of one is not the same as the data structure of another, even though some of the content of the records is substantially the same. For example, one database may store names and addresses in the following fields: FIRST₋₋ NAME, LAST₋₋ NAME, and ADDRESS. Another database may, however, store the same information with the following structure: NAME, STREET₋₋ NO., STREET₋₋ NAME, CITY₋₋ STATE, and ZIP. Although the content of the records is intended to contain the same kind of information, the organization of that information is completely different.

It is often the case that users of incompatible databases want to be able to synchronize the databases. For example, in the context of scheduling and contact manager Applications, a person might use one Application on the desktop computer at work while another on his handheld computer or his laptop computer at home. It is desirable for many of these users to be able to synchronize the entries on one with entries on another. However, the incompatibility of the two databases creates many problems that need to be solved for successful synchronization. The U.S. patent and copending patent application of the assignee hereof, Puma Technology, Inc. of San Jose, Calif. (U.S. Pat. No. 5,392,390; U.S. application, Ser. No. 08/371,194, filed on Jan. 11, 1995, incorporated by reference herein) show two methods for synchronizing incompatible databases and solving some of the problems arising from incompatibility of databases. However, other problems remain.

Some database Application run on computer systems with very limited storage capacity, such as handheld computers. It is often desirable to synchronize the databases on these devices with databases on larger computers such as desktop computers which have much higher storage capacity. However, a straight synchronization between the Applications on the two devices may result in storage capacity of the smaller devices being mostly consumed with the records from the larger device, rendering the smaller device inoperable.

SUMMARY OF THE INVENTION

The invention solves the difficulty of synchronizing databases in which events are maintained across different date ranges. A date range is set for which synchronization will take place. Records falling outside of the date range are not synchronized. The date range of the prior synchronization is stored, and a current synchronization is performed across the combination of the current and prior date ranges. The problems of synchronization software attempting to fill a smaller capacity device with events across a wide date range that can only practically be stored on a larger capacity device are avoided.

The invention features a computer implemented method of synchronizing at least a first and a second database each containing dated records such as events, wherein the records of the first database extend across a narrow date range narrower than the date range of the records of the second database. A prior synchronization is performed across a prior date range set using the date of the prior synchronization and the narrow date range. The date range of the prior synchronization is stored, along with the history file containing information representative of the content of the databases following the prior synchronization. When a current synchronization is performed, it is performed across a date range that combines the prior date range with a current date range set using the date of the current synchronization and the narrow date range.

The invention may be implemented in hardware or software, or a combination of both. Preferably, the technique is implemented in computer programs executing on programmable computers that each include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. Program code is applied to data entered using the input device to perform the functions described above and to generate output information. The output information is applied to one or more output devices.

Each program is preferably implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the programs can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language.

Each such computer program is preferably stored on a storage medium or device (e.g., ROM or magnetic diskette) that is readable by a general or special purpose programmable computer for configuring and operating the computer when the storage medium or device is read by the computer to perform the procedures described in this document. The system may also be considered to be implemented as a computer-readable storage medium, configured with a computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner.

Other features and advantages of the invention will become apparent from the following description of preferred embodiments, including the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic drawing of the various modules constituting the preferred embodiment.

FIG. 2 is a representation of the Workspace data array.

FIG. 3 is the pseudocode for the Translation Engine Control Module.

FIG. 4 is the pseudocode for generating the parameter Table.

FIG. 5 is the pseudocode for fanning a recurring record.

FIG. 6 is the pseudocode for the Synchronizer loading the History File.

FIG. 7 is the pseudocode for matching key fields (Key₋₋ Field₋₋ Match).

FIG. 8 is the pseudocode for loading records of B₋₋ Database into Workspace.

FIG. 9 is the pseudocode for A₋₋ Sanitization of B₋₋ Database records in Workspace.

FIG. 10 is the Pseudocode for a specific example of a rule of data value used for sanitization.

FIG. 11 is the pseudocode for orientation analysis.

FIG. 12 is the pseudocode for Conflict Analysis And Resolution (CAAR).

FIG. 13 is the pseudocode for analyzing unique ID bearing Fanned Instance Groups (FIGs).

FIG. 14 is the pseudocode for expanding CIGs created from unique ID bearing records.

FIG. 15 is the pseudocode for finding weak matches for a record.

FIG. 16 is the pseudocode for finding matches between recurring items and non₋₋ unique ID bearing instances.

FIG. 17 is the pseudocode for completing Same Key Group (SKG) analysis.

FIG. 18 is the pseudocode for setting the Maximum₋₋ CIG₋₋ Size for every CIG analyzed in FIG. 17.

FIG. 19 is the pseudocode for setting CIG₋₋ Types.

FIG. 20 is the User Interface for conflict resolution when the Notify option is selected.

FIG. 21 is the pseudocode for merging exclusion lists.

FIG. 22 is a look up table used by the function in FIG. 21.

FIG. 23 is a look up table used by the function in FIG. 21.

FIG. 24 is a look up table used by the function in FIG. 21.

FIG. 25 is a pseudocode for unloading records from Workspace to a non-rebuild-all database.

FIG. 26 is the look up table for determining unloading outcome results.

FIG. 27 is the pseudocode for fanning recurring records of A-Database for unloading.

FIG. 28 is the pseudocode for unloading the History File.

FIG. 29 is a table showing cases for fanning Recurring Masters into own database.

FIG. 30 is the pseudocode for loading records by a fast synchronization Translator.

FIG. 31 is the pseudocoe for loadin records by a fast synchronization Translator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows the relationship between the various modules of the preferred embodiment. Translation Engine 1 comprises Control Module 2 and Parameters Table Generator 3. Control Module 2 is responsible for controlling the synchronizing process by instructing various modules to perform specific tasks on the records of the two databases being synchronized. The steps taken by this module are demonstrated in FIG. 3. The Parameters Table Generator 3 is responsible for creating a Parameter₋₋ Table 4 which is used by all other modules for synchronizing the databases. Details of the Parameter₋₋ Table are described in more detail below. The Synchronizer 15 has primary responsibility for carrying out the core synchronizing functions. It is a table-driven code which is capable of synchronizing various types of databases whose characteristics are provided in the Parameter₋₋ Table 4. The Synchronizer creates and uses the Workspace 16, which is a temporary data array used during the synchronization process.

A Translator 5 (A₋₋ Translator) is assigned to the A₋₋ database 13 and another Translator 9 (B₋₋ Translator) to the B₋₋ database 14. Each of the database Translators 5 and 9 comprises three modules: Reader modules 6 and 10 (A₋₋ Reader and B₋₋ Reader), which read the data from the databases 13 and 14; Unloader modules 8 and 12 (A₋₋ Unloader and B₋₋ Unloader), which analyze and unload records from the Workspace into the databases 13 and 14; and Sanitizing modules 7 and 11 (A₋₋ Sanitizer and B₋₋ Sanitizer), which analyze the records of the other database loaded into the Workspace and modify them according to rules of data value of its own database. In the preferred embodiment, the modules of the A₋₋ Translator 5 are designed specifically for interacting with the A₋₋ database 13 and the A₋₋ Application 17. Their design is specifically based on the record and field structures and the rules of data value imposed on them by the A₋₋ Application, the Application Program Interface (API) requirements and limitations of the A₋₋ Application and other characteristics of A₋₋ Database and A₋₋ Application. The same is true of the modules of B₋₋ Translator 9. These Translators are not able to interact with any other databases or Applications. They are only aware of the characteristics of the database and the Application for which they have been designed. Therefore, in the preferred embodiment, when the user chooses two Applications for synchronization, the Translation Engine chooses the two Translators which are able to interact with those Applications. In an alternate embodiment, the translator can be designed as a table-driven code, where a general Translator is able to interact with a variety of Applications and databases based on the parameters supplied by the Translation Engine 1.

Referring to FIGS. 1, 2 and 3, the synchronization process is as follows. The Parameter₋₋ Table 4 is generated by the Parameter Table Generator 3. The Synchronizer 15 then creates the Workspace 16 data array and loads the History File 19 into the Workspace 16. The B₋₋ Reader module 11 of the B₋₋ Translator reads the B₋₋ database records and sends them to the Synchronizer for writing into the Workspace. Following the loading of B₋₋ Database records, the A₋₋ Sanitizer module 8 of the A₋₋ Translator 5 sanitizes the B₋₋ Records in the Workspace. The A₋₋ Reader module 7 of the A₋₋ Translator 5 then reads the A₋₋ Database records and sends them to the Synchronizer 16 for writing into the Workspace. The B₋₋ Sanitizer module 12 of the B₋₋ Translator 9 then sanitizes the A₋₋ Records in the Workspace. The Synchronizer then performs the Conflict Analysis and Resolution (CAAR) on the records in Workspace. At the end of this analysis the user is asked whether he/she would like to proceed with updating the A₋₋ and B₋₋ databases. If so, the B₋₋ Unloader module of the B₋₋ Translator unloads the appropriate records into the B₋₋ database. The A₋₋ Unloader module 6 then performs the same task for the A₋₋ Database. Finally, the Synchronizer creates a new History File 19.

FIG. 3 is the pseudocode for the preferred embodiment of the Control Module 2 of the Translation Engine 1. Control Module 2 first instructs the Parameter Table Generator 3 of the Translation Engine 1 to create the Parameter₋₋ Table (Step 100). FIG. 4 is the pseudocode for the preferred embodiment of the Parameter Table Generator module 3. The user is first asked to choose whether to use a previously chosen and stored set of preferences or to enter a new set of preferences (Step 150). Steps 151-165 show the steps in which the user inputs his/her new preferences. In step 152, the user chooses whether to perform a synchronization from scratch or an incremental synchronization. In a synchronization from scratch, synchronization is performed as if this was the first time the two databases were being synchronized. In an incremental synchronization, the History File from the previous file is used to assist with synchronization. The user will likely choose incremental synchronization if there has been a prior synchronization, but the user may choose to synchronize from scratch where the user would like to start with a clean slate (perhaps due to significant change in the nature of the data in the databases). The user then selects the two Applications and related databases (A₋₋ Database and B₋₋ Database) to be synchronized (step 153). The user then chooses (step 154) whether the Synchronizer should use the default field mapping for those two databases during synchronization or the user will modify the field mapping. Field mapping is generally described in U.S. Pat. No. 5,392,390 (incorporated by reference). In accordance with the user's preferences, the Parameter Table Generator then stores the appropriate A₋₋ Database to B₋₋ Database fields map (A→B₋₋ Map) and B₋₋ Database to A₋₋ Database fields map (B→A₋₋ Map) in the Parameter₋₋ Table (Steps 155-158 and 159-163, accordingly).

If in step 150 the user selected to use previously chosen and stored set of preferences (steps 166-171), those preferences are loaded and stored in the Parameter₋₋ Table (steps 169-170).

In case of date bearing records such as appointments and ToDo lists, the user enters the date range for which the user wants the records to be synchronized (step 172). The preferred embodiment allows the user to use relative date ranges (Automatic₋₋ Date₋₋ Range) (substeps 171(a) and (b)). For example, the user can select the date range to be 30 days into the past from today's date and 60 days into the future from today's date. The Parameter Table Generator 3 then calculates and stores in the Parameter₋₋ Table the Start₋₋ Current₋₋ Date₋₋ Range and End₋₋ Current₋₋ Date₋₋ Range values, the two variables indicating the starting point and the ending point of the date range for the current synchronization session (step 173-174).

In steps 174 and 175, various parameters identifying the characteristics of the A₋₋ Database and Application and B₋₋ Database and Application are loaded from a database (not shown) holding such data for different Applications. These are in turn stored in the Parameter Table. One of the sets of parameters loaded and stored in the Parameter₋₋ Table is the Field₋₋ List for the two databases. The Field₋₋ List₋₋ A and Field₋₋ List₋₋ B contain the following information about each field in the data structure of the two databases:

1. Field name.

2. Field Type.

3. Field Limitations.

4. No₋₋ Reconcile Flag.

6. Key₋₋ Field Flag.

7. Mapped₋₋ Field Flag.

Field name is the name given to the field which the Translator for this Application uses. This name may also be the name used by the Application. Field Type identifies to the Synchronizer 15 the nature of the data in a field, e.g., Data, Time, Boolean, Text, Number, or Binary. The Field Name does not supply this information to the Synchronizer. Field Limitations identifies the various limitations the database manager imposes on the contents of a field. These limitations include: maximum length of text fields, whether the text field must be in upper-case, range of permissible values (for example, in ToDo records priority field, the range of permissible values may be limited from 1 to 4), and whether a single line or multiple line field.

No₋₋ Reconcile flag indicates whether a field is a No₋₋ Reconcile field, meaning that it will not be used to match records nor will it be synchronized although it will be mapped and possibly used in synchronization. Almost all fields will not be designated as No Reconcile. However, sometimes it is necessary to do so. Key₋₋ Field flag indicates that a field should be considered as a key field by the Synchronizer 15.

Key fields are used by the Synchronizer in various stages of synchronization as will be discussed in detail below. The decision of identifying certain fields as key is based on examining the various Applications to be synchronized, their data structure, and the purpose for which the database is used. Such examination reveals which fields would best function as key fields for synchronization. For example, for an address book database, the lastname, firstname, and company name field may be chosen as key fields. For Appointments, the date field and the description field may be chosen as key fields.

Mapped₋₋ Field flag indicates whether a field is mapped at all. The Synchronizer uses this flag to determine whether it should use the A→B₋₋ Map or B→A₋₋ Map to map this field. Unlike a No₋₋ Reconcile field, an unmapped field will not be carried along through the synchronization.

Another set of parameters in the Parameter₋₋ Table identify the Translator Modules 13, 14 for the two Applications which the user has selected. Because each Application is assigned its own Translator, it is necessary to identify to the Command Module and the Synchronizer which Translators should be used.

In step 102 of FIG. 1, the Translation Engine instructs the Synchronizer to load the History File. History File is the file which was saved at the end of last synchronization. It contains the history of the previous synchronization which is necessary for use with the current synchronization in case of Incremental Synchronization. Records from the A₋₋ Database and B₋₋ Database are analyzed against the records of the history file to determine the changes, additions, and deletions in each of two databases since last synchronization and whether additions, deletions, or updates need to be done to the records of the databases. Referring to FIG. 5, in steps 200-201, the Synchronizer finds the appropriate History file to be loaded. If Synchronization₋₋ from₋₋ Scratch flag is set, the History File is deleted (step 203). If no History File is found, the synchronization will proceed as if it was a synchronization from scratch (step 204). If the Field Lists stored in the History File are not the same as the current Field Lists in the Parameter₋₋ Table, or the mapping information is not the same, the synchronization will proceed as synchronization from scratch because the differences indicate that the History File records will not properly match the database records (steps 206-209).

In step 210, the Synchronizer uses the Field₋₋ List for database B to create the Workspace 16. It is a large record array which the Synchronizer uses during synchronization. Referring to FIG. 2, Workspace 16 consist of two sections. First, the Synchronizer uses the Field List for the B₋₋ Database to make a record array 21 which has all the characteristics of the B₋₋ Database record structure. In addition, in each record in the Workspace, certain internal fields are added. One field is ₋₋ subtype containing Origin Tags. Two other fields, called Rep₋₋ Basic and Rep₋₋ Excl, are included for all Appointment and ToDo Sections. The Rep₋₋ Basic field gives a full description of the recurrence pattern of a recurring record. It includes the following parameters:

1. Basic₋₋ Repeat₋₋ Type

2. Frequency

3. StopDate

4. other parameters

5. Rep₋₋ Excl

Basic₋₋ Repeat₋₋ Type contains the variable which indicates whether the recurring record is a daily, weekly, monthly (same date each month), monthly by position (e.g., 3rd Friday of each month), yearly (e.g., July 4th each year), yearly by Position (e.g., 3rd Friday of September each year), quarterly, etc. This variable is set to No₋₋ Repeat for non-recurring records.

Frequency indicates whether the pattern is, for example, for every week, every other week, etc. StartDate and StopDate show the first date and last date in the pattern. Some other parameters in the Rep₋₋ Basic include, for example, a list of days to be included for the pattern (e.g. I plan to hold a weekly staff meeting every Thursday starting Nov. 15, 1997.)

Rep₋₋ Excl is the exclusion list. It is a list of dates which at some point belonged to the recurring record, but have since been deleted or modified and no longer are an event represented by the recurring record.

Since some databases do not provide for recurring types of records, the synchronization process sometimes must create single records for each of the instances of a recurring record for those databases. For example, for a recurring lunch every Thursday, the synchronization must produce a single record for each Thursday in such a database. This is accomplished by the process of fanning which uses Rep₋₋ Basic. Each of those instances is called a fanned instance. FIG. 6 sets out the preferred embodiment of the process of fanning a record.

Fanning of recurring records also takes into account another set of considerations regarding date range limitations and usefulness of instances to the user.

First, fanning is limited to the applicable date range. Second, the number of fanned instances is limited. When synchronizing Databases A and B, the preferred embodiment permits different sets of limits on fanned instances to be established for each Database. This, for example, assists with managing storage capacity of a memory-constrained handheld device when being synchronized with a database on a desktop PC.

If the current Date Range is large enough to accommodate more than the maximum number of instances which might be generated, those instances will be chosen which are likely to be most useful to the user. In the preferred embodiment, it is assumed that future instances are always more useful than past instances, that near future instances are more useful than distant future instances, and that recent past instances are more useful than distant past instances. Therefore, based on these assumptions, a fanning date range is calculated (FIG. 6, step 236).

Referring to FIG. 2, in the second step of creating the Workspace, the Synchronizer establishes an Extended Index Array 20 which has an index entry associated with each entry in the record array. Each index contains the following variables:

1. Next₋₋ In₋₋ CIG:

2. Next₋₋ In₋₋ SKG:

3. Next₋₋ In₋₋ FIG

4. Key₋₋ Field₋₋ Hash

5. A₋₋ Unique₋₋ ID₋₋ Hash

6. B₋₋ Unique₋₋ ID₋₋ Hash

7. Non₋₋ Key₋₋ Field₋₋ Hash

8. Non₋₋ Date₋₋ Hash

9. Exclusion₋₋ List₋₋ Hash

10. Start₋₋ Date&Time

11. End₋₋ Date&Time

12. Various bit flags

Next₋₋ In₋₋ CIG is a linkage word, pointing to next member of the same Corresponding Item Group (CIG). A CIG is a group of records, one from each database and the History File, if applicable, which represent the same entry in each of the databases and the History File. There may be one, two or three records in a CIG. Next₋₋ In₋₋ SKG is a linkage word, pointing to next member of the Same Key Fields Group (SKG). An SKG is a group of records having the same key fields. Next₋₋ In₋₋ FIG is a linkage word, pointing to the next member of the Fanned Instances Group (FIG). A FIG is the group of fanned instances which correspond to a single recurring record.

Key₋₋ Field₋₋ Hash is hash of all Key₋₋ Fields. A₋₋ unique₋₋ ID₋₋ Hash is hash of unique ID, if any, assigned by A₋₋ Database. B₋₋ unique₋₋ ID₋₋ Hash is hash of unique ID, if any, assigned by B₋₋ Database. Non₋₋ Key₋₋ Field₋₋ Hash is hash of all Non-Key Match Field, a Match Field being any mapped field which is not flagged as No₋₋ Reconcile. Non₋₋ Date₋₋ Hash is hash of all Non-Date Non-Key Match Fields. Exclusion₋₋ List₋₋ Hash is hash of recurring record's exclusion list.

Start₋₋ Date&Time and End₋₋ Date&Time are used for Appointment and ToDo type record only, indicating the start and end date and time of the record. They are used to speed up comparing functions throughout the synchronization. Hash values are also used to speed up the process of comparison. The preferred embodiment uses integer hashes. Hash value computation takes into account certain rules of data value for fields, as will be described in more detail below.

In the preferred embodiment, the record array 21 is stored on magnetic disk of a computer whereas the Extended Index 20 is held resident in memory. The Extended Indexes have record pointer fields which point to each of the records on the disk file.

The Control Module 2 now instructs the synchronizer to load the History File into the Workspace (FIG. 3, step 102). Referring to FIG. 6, the synchronizer loads the records beginning in first available spot in the Workspace (step 211). The Synchronizer then performs an analysis on each of the records and resets some of the values in the records (steps 212-228). The records are also checked against the current date range and those falling outside of it are marked appropriately for Fast synchronization function, which will be described below. In case of recurring records, if any of the instances is within the current date range, then the recurring record itself will be considered within the current date range (steps 217-227).

The synchronizer then builds SKGs by finding for each history record one record which has matching key fields and by placing that record in the SKG of the history record (step 215-216). Referring to FIG. 7, steps 250-258 describe the Key₋₋ Field₋₋ Match function used for matching records for SKG.

When comparing two records or two fields, in the preferred embodiment, the COMPARE function is used. The COMPARE function is intelligent comparison logic, which takes into account some of the differences between the rules of data value imposed by the A₋₋ Application and the B₋₋ Application on their respective databases. Some examples are as follows. The COMPARE function is insensitive to upper and lower case letters if case insensitive field attribute is present. Because some Applications require entries to be in all capital letter, the COMPARE function ignores the differences between upper and lowercase letters. The COMPARE function takes into account any text length limitations. For example, when comparing "App" in the A₋₋ Database and "Apple" in the B₋₋ Database, the COMPARE function takes into account that this field is limited to only 3 characters in the A₋₋ Database. It also takes into account limits on numerical value. For example, priority fields in the A₋₋ Application may be limited to only values up to 3, whereas in the B₋₋ Application there may not be any limitation. The COMPARE function would treat all values in B₋₋ records above 3 as 3.

The COMPARE function may ignore various codes such as end of line characters. It may strip punctuation from some fields such as telephone numbers and trailing white space from text fields (i.e "Hello " is treated as "Hello"). It also considers field mapping. For example, if the only line that is mapped by the A→B Map is the first line of a field, then only that line is compared. When comparing appointment fields, because different databases handle alarm date and time differently when Alarmflag is false, the COMPARE function treats them as equal even though the values in them are not the same. It skips Alarm Date and Time, if the Alarm Flag is False. It also ignores exclusion lists when comparing recurring records.

In an alternate embodiment, the COMPARE function may take into account more complicated rules for data value of the two Applications, such as the rules for data value imposed by Microsoft Schedule+, described above. Such a COMPARE function may be implemented as a table driven code, the table containing the rules imposed by the A₋₋ Application and the B₋₋ Application. Because the COMPARE function has a specific comparison logic and takes into account a number of rules, the hashing logic must also follow the same rules. It should be noted that the COMPARE function is used throughout the preferred embodiment for field comparisons.

Now that the History File is loaded into the Workspace, the Control Module 2 instructs the B₋₋ Translator 13 to load the B₋₋ Database records (FIG. 3, step 103). Referring to FIG. 8, steps 300-308, the B₋₋ Reader module 11 of the B₋₋ Translator 13 loads each B₋₋ record which has the right Origin Tag, which will be explained in more detail below.

The record must also be within the loading date range, which is a concatenation of the previous and current date ranges. The B₋₋ Translator sends these records to the Synchronizer which in turn stores them in the Workspace. When synchronizing with a date range limitation, all records which fall within either the previous or the current date ranges are loaded. The current date range is used during unloading to limit the unloading of the records to only those records which fall within the database's current date range. In an alternate embodiment of the invention, each database or Application can have its own date range for each synchronization.

Most Applications or databases permit record-specific and field-specific updates to a Database. But some Applications or databases do not. Instead the Translator for these Application must re-create the whole database from scratch when unloading at the end of synchronization. These databases are identified as Rebuild₋₋ All databases. To accommodate this requirement all records from such a database must be loaded into the Workspace, so that they can later be used to rebuild the whole database. These databases records, which would otherwise have been filtered out by the date range or the wrong origin tag filters, are instead marked with special flag bits as Out₋₋ Of₋₋ Range or Wrong₋₋ Section₋₋ Subtype. These records will be ignored during the synchronization process but will be written back unmodified into the database from which they came by the responsible Unloader module 6, 10.

Control Module 2 next instructs the A₋₋ Translator 5 to sanitize the B-records. Referring to FIG. 9, steps 350-361, the A₋₋ Sanitizer module 8 of the A₋₋ Translator 5 is designed to take a record having the form of an A₋₋ Record and make it conform to the specific rules of data value imposed by the A₋₋ Application on records of the A₋₋ Database. A₋₋ Sanitizer is not aware which database's field and records it is making to conform to its own Application's format. It is only aware of the A₋₋ Application's field and record structure or data structure. Therefore, when it requests a field from the sanitizer using the A₋₋ Database field name, it is asking for fields having the A₋₋ Database data structure. The Synchronizer, in steps 375-387, therefore maps each record according to the B→A₋₋ Map. In turn, when the Synchronizer receives the fields from the A₋₋ SANITIZER, it waits until it assembles a whole record (by keeping the values in a cache) and then maps the record back into the B format using the A→B₋₋ Map.

How a record or a field is sanitized in step 354 and 357 depends on the rules of data value imposed by the A₋₋ Application. For example, all of the logic of intelligent comparison in the COMPARE function described above can be implemented by sanitization. However, sanitization is best suited for more complex or unique types of database rules for data value. For example, consider the Schedule+ rules regarding alarm bearing Tasks records described above. FIG. 10 shows a sanitization method for making records of incompatible databases conform to the requirements of Schedule+. Without sanitization, when a Tasks record of a Schedule+ database is compared to its corresponding record in another database, the Tasks record may be updated in fields which should be blank according to the Schedule+ rules of data value. Such an update may possibly affect the proper operation of Schedule+ after synchronization.

Referring to FIG. 11, following sanitization of all B₋₋ Records into the Workspace, the Synchronizer sets the values for the Extended Index of each record based on the record's values (steps 451-459). Also if the records in the B₋₋ Database bear a unique ID, and matches for those unique IDs are found in the H₋₋ Records in the Workspace, the two records are joined in a CIG because they represent the same record in both History File and B₋₋ Database (step 462). The record is also joined to an SKG it may belong to (step 464). The loading of B₋₋ Records is now complete.

The Control Module 2 of the Translation Engine 3 now instructs the A₋₋ Translator 5 to load the records from the A₋₋ Database (step 105). The loading process for the A₋₋ Records is the same as the loading process for the B₋₋ Database, except for some differences arising from the fact that records in the Workspace are stored according to the B₋₋ Database data structure. Therefore, as the synchronizer 15 receives each A₋₋ record from the A₋₋ Reader module 7 of the A₋₋ Translator 5, the Synchronizer maps that record using the A→B₋₋ Map before writing the record into the next available spot in the Workspace. Since the A₋₋ records are mapped into the B₋₋ Record format, when the B₋₋ Sanitizer is instructed by the Control Module 2 to begin sanitizing those records and starts asking for them from the synchronizer, they already have the B₋₋ Database format. Therefore, the synchronizer 15 does not need to map them before sending them to the B₋₋ Sanitizer module 12 of the B₋₋ Translator 19. For the same reason, there is no need for them to be mapped once they are sent back by the B₋₋ Sanitizer after having been sanitized. Once all the records are loaded, the records will undergo the same orientation analysis that the B₋₋ Records underwent (FIG. 11).

At this point, all records are loaded into the Workspace. SKGs are complete since every record at the time of loading is connected to the appropriate SKG. CIGs now contain all records that could be matched based on unique IDs. At this point, the records in the Workspace will be analyzed according to Conflict Analysis and Resolution ("CAAR") which is set out in FIG. 12 and in more detail in FIGS. 13-18 and corresponding detailed description.

First, in step 500, ID bearing fanned instances in the History File records are matched to the fanned instances in the ID bearing database from which they came. The records from the database which have remained unchanged are formed into a new FIG. A new Synthetic Master is created based on those records and joined to them. The records which have been changed or deleted since last synchronization are set free as single records. They also result in a new exclusion list being created based on an old exclusion list and these new single records.

Second, in step 501, matches are sought for the ID based CIGs which are the only CIGs so far created in order to increase the membership of those CIGs. Preferably an exact all fields match is sought between current members of a CIG and a new one. Failing that, a weaker match is sought.

Third, in step 502, master/instances match is sought between recurring records and non-unique ID bearing instances by trying to find the largest group of instances which match certain values in the Recurring Master.

Fourth, in step 503, the items remaining in the SKGs are matched up based on either exact all field match or master/instance match, or a weaker match.

Fifth, in step 501, the appropriate CIG₋₋ Types are set for all the CIGs. CIG₋₋ Types will determine what the outcome of unloading the records will be.

Referring to FIG. 13, first step in CAAR is analyzing unique ID bearing Fanned Instance Groups. This analysis attempts to optimize using unique IDs assigned by databases in analyzing fanned instances of recurring records.

The analysis is performed for all Recurring Masters (i.e. all recurring records) which have ID-bearing fanned instances (or FIG records) in the H₋₋ File (step 550). All FIG records in the History File associated with a Recurring Master are analyzed (steps 551-559). They are all removed from the SKG. If a FIG record is a singleton CIG, it means that it was deleted from the database since the previous synchronization. Therefore, it is added to the New₋₋ Exclusion₋₋ List (step 553). If a FIG record is a doubleton and is an exact match, it means that the record was not modified since the previous synchronization. In this case, the record from the database is also removed from SKG (step 555). If a FIG record is a doubleton but is not an exact match for its counterpart in the database, it means that the record was changed in the database. The History File record is treated as a deletion and therefore added to the New₋₋ Exclusion₋₋ List. The modified record in the database, which does not match the recurring record any longer, is treated as a free standing record un-associated with the Recurring Master (step 557).

Upon analysis of all FIG records, a new record, the Synthetic Master, is created and joined in a CIG with the Recurring Master (step 231-236). The Synthetic Master has the same characteristics as the Recurring Master, except that it has a new exclusion list which is a merger of the New₋₋ Exclusion₋₋ List and the Exclusion₋₋ List of the Recurring Master (step 563). Also a new FIG is created between the Synthetic Master and the CIG-mates of all FIG records from the History File (step 565).

In steps 567-569, the Synchronizer checks to see if there are some instances of the Recurring Master which fall within the previous synchronization's date range but fall outside of the current synchronization's date range. If so, the Fan₋₋ Out₋₋ Creep flag is set, indicating that the date range has moved in such a way as to require the record to be fanned for the database before unloading the record. The Fan₋₋ Out₋₋ Creep flag is an increase in the value in the Non₋₋ Key₋₋ Field Hash of the Recurring Master. In this way, the Recurring Master during the unloading of the records will appear as having been updated since the last synchronization and therefore will be fanned for the current date range.

In step 570, all the FIG records analyzed or created in this analysis are marked as Dependent₋₋ FIGs. This results in these records being ignored in future analysis except when the recurring records to which they are attached are being analyzed.

At the end of the above analysis, all the records having a unique ID assigned by their databases have been matched based on their unique ID. From this point onward, the records which do not have unique IDs must be matched to other records based on their field values. In the preferred embodiment, there are two categories of field value matches: strong matches and weak matches. A strong match between two records that have matching key fields is when non-key fields of the two records match or it is a Recurring Master and a fanned instance match (FIG. 14, steps 606-610). Referring to FIG. 15, a weak match between two records that have matching key fields is when the following are true: each of the two records are from different origins, because two records from the same source should not be in a CIG (e.g., A₋₋ Database and History File); each is not a weak match for another record because there is no reason to prefer one weak match over another; each is not a Dependent₋₋ FIG since these records do not have an independant existence from their recurring masters; both records are either recurring or nonrecurring since a recurring and a nonrecurring should not be matched except if one is an instance of the other in which case it is a strong match; and, in case of non-recurring, they have matching Key₋₋ Date₋₋ Field which is the same as the Start₋₋ Date in the preferred embodiment because items on the same date are more likely to be modified versions of one another.

Referring to FIG. 14, these two types of matching are used to match records to existing CIGs for History File records which have been created based on matching unique IDs. Only doubleton CIGs are looked at, because singleton CIGs are handled in step 504 of FIG. 12 and tripleton CIGs are complete (steps 601-604). If a strong match is found, then if the record was a weak match in another CIG, it is removed from that CIG, and new weak match is found for that CIG (612-614). While weak matches are left in SKGs in case they will find a strong match, strong matches are removed from their SKGs (step 614). If a strong match is not found, then a weak match is sought (steps 617-620). All records in the CIG are removed from SKG if no weak match is found, because this means that there is no possibility of even a weak match for this record (step 619).

The next step in CAAR is finding non-unique ID bearing instances for recurring items (FIG. 12, step 503). Referring to FIG. 16, this analysis takes place only if the database from which instances matching a recurring record are sought does not provide unique ID or if we are synchronizing from scratch (steps 650-653). The goal of this analysis is to find matching instances for each Recurring Master from a different source than the Recurring Master. This analysis counts the number of records in SKG of the Recurring Master which have matching Non₋₋ Date₋₋ Hash value (steps 665-669). The group of matching SKG records having the same non₋₋ Date₋₋ Hash value and having the highest number of members (if the number of members exceeds 30% of unexcluded instances) is then formed into a Homogeneous₋₋ Instances₋₋ Group (steps 670-672). A Synthetic Master is created using the Rep₋₋ Basic of the Recurring Master and using the values from the homogeneous instances group. An Exclusion list is created based on the items belonging to the recurrence pattern but missing from the Homogeneous₋₋ Instances₋₋ Group. The Synthetic Master is added to the CIG of the Recurring Master (steps 673-678). A new FIG for the Synthetic Master is then created using the Homogeneous₋₋ Instances₋₋ Group (step 679). These records are removed from any CIGs to which they belonged as weak matches and new weak matches are sought for those CIGs (steps 680-684). Since the records in Homogeneous₋₋ Instances₋₋ Group have now been matched to a recurring record, they are marked as Dependent₋₋ FIGs (step 683). The Recurring Master's CIG is then marked with Fan₋₋ Out₋₋ Creep flag, if necessary (step 685).

The next step in CAAR is completing analysis of records in SKGs (FIG. 12, step 504). Referring to FIG. 17, this analysis attempts to increase the population of CIGs up to a maximum by finding key field based matches with records from a source different from those of the CIG records. This analysis is performed by analyzing all the records in the SKGs except for the singleton SKGs (steps 703 and 712). The first thing is to remove any members that have already been marked as WEAK matches attached to ID-based doubleton CIGs. Those are left in the SKG up to this point to allow for the possibility that a STRONG match would be found instead. But that is not possible any longer (steps 713-715). Once the weak matches have been removed, all remaining SKG members belong to singleton CIGs. Any non-singleton CIGs which are formed from here on will be purely key field based.

Throughout the remaining SKG Analysis we are careful not to seek H₋₋ Record-A₋₋ Record or H₋₋ Record-B₋₋ Record matches for unique ID-bearing Source, since that would violate the exclusively ID-based matching scheme that applies in such cases. Note however that an A₋₋ Record-B₋₋ Record match is acceptable even if both A₋₋ Database and B₋₋ Database are unique ID-bearing databases.

Given that Key Field should not be performed where ID based matches are available (or otherwise there may be matches between records with differing IDs), there are limits to how big CIGs can get at this point. If both A and B₋₋ Databases are unique ID-bearing, any remaining H₋₋ Record must remain in Singleton CIGS, because they are prohibited from forming key fields based matches with items from either databases. Such H₋₋ Records are simply removed from the SKG when they are encountered. If just one of the two databases being synchronized is unique ID-bearing then the maximum population that any CIG can now attain is 2 (FIG. 18, steps 750-751). If neither database is unique ID bearing then the CIG₋₋ Max₋₋ Size is three. For every CIG which is analyzed in FIG. 17, the CIG₋₋ Max₋₋ Size is set according to this logic. When a CIG reaches its maximum possible population all of its members are removed from the appropriate SKG.

First, strong matches for the H-records are searched for, before trying to find A-B matches. If both Databases are non-unique ID-bearing then two strong matches for each H₋₋ Record, an H-A and an H-B match, are sought (steps 715-720). If finding a strong match results in reaching the CIG₋₋ Max₋₋ Size, all members of the CIG are removed from the SKG (step 721).

When maximum CIG population is 3, weak matches are sought for strong matching CIG doubleton in order to build triplet CIGs. The first weakly matching SKG member is added to the CIG (steps 722-728). Whether or not a weak match is found for any of the doubleton CIGs, its members are removed from the SKG (step 726). As there are no strong matches left in the SKG, weak matches are found for any remaining SKG members and joined to them in CIGs (steps 722-725).

At this stage, all CIGs are built. They must now be examined to determine what needs to be done to these records so that the databases are synchronized, i.e. whether the records in the CIGs need to be added, deleted or changed in the two databases. First step is determining the CIG₋₋ TYPE which represents the relation between the records. The following CIG types are defined, all using a 3-digit number that represents values found for A₋₋ DATABASE, History File, and B₋₋ Database, respectively:

1. 001--record is "new" in the B₋₋ DATABASE

2. 010--record is present in History, but absent in both A₋₋ Database and B₋₋ Databases

3. 100--record is "new" in the A₋₋ Database

4. 101--record is "new" in both A₋₋ Database and B₋₋ DATABASE; same in both

5. 102--record is "new" in both A₋₋ Database and B₋₋ DATABASE; different in each (conflict)

6. 110--record deleted from B₋₋ DATABASE

7. 011--record deleted from A₋₋ Database

8. 012--record deleted from A₋₋ Database and changed on B₋₋ DATABASE (DEL vs CHANGE conflict)

9. 210--record changed on A₋₋ Database and deleted from B₋₋ DATABASE(DEL vs CHANGE conflict)

10. 111--record unchanged since previous synchronization

11. 112--record changed on B₋₋ DATABASE only since previous synchronization

12. 211--record changed on A₋₋ Database only since previous synchronization

13. 212--record changed identically on both since previous synchronization

14. 213--record changed differently on each since previous synchronization (conflict)

15. 132--a conflict (102 or 213) was resolved by forming a compromise value; Update both

16. 13F--created when a 132 Update both CIG is Fanned into the B₋₋ DATABASE

FIG. 19 shows the method used for setting all except the last two CIG₋₋ Types which are set in other operations.

Four of the CIG types assigned above involve conflicts: 102, 213, 012, and 210. Conflicts are those instances where a specific conflict resolution rule chosen by the user or set by default, or the user's case by case decision, must be used to determine how the records from the databases should be synchronized. CIG types 012 and 210 are cases where a previously synchronized record is changed on one side and deleted on the other. In the preferred embodiment, such conflicts are resolved according to the rule that CHANGE overrules the DELETE. So the net result for CIG type 012 is to add a new record to the A₋₋ Database to match the record in the B₋₋ DATABASE. The reverse is true for CIG type 210, where a new record is added to the B₋₋ Database. In an alternate embodiment, the user may be allowed to register an automatic preference for how to resolve such conflicts or decide on a case-by-case basis a conflict resolution option.

The other two conflict types--102 and 213--are resolved in the preferred embodiment according to the Conflict Resolution Option established by the user. First, the user may choose to ignore the conflict. This option leaves all 102 and 213 conflicts unresolved. Every time synchronization is repeated the conflict will be detected again and ignored again, as long as this option remains in effect and as long as the conflicting records are not changed by other means.

The user may choose to add a new record to each of the two databases. This option resolves 102 and 213 conflicts by adding the new A₋₋ Record to the B₋₋ Database, and adding the new B₋₋ Record to the A₋₋ Database. This option is implemented by breaking a 102 CIG into two separate CIGs (types 100 and 001) and a 213 CIG into three separate CIGs (types 100, 010, and 001). Subsequent processing of those descendant CIGs causes new records to be added across and stored in the History File.

The user may elect that A₋₋ Database records should always trump or win over B₋₋ database records. This option is implemented by changing the CIG type to 211--the processing during unloading the records changes the record value in the B₋₋ Database to match the current record value in the A₋₋ Database.

The user may elect that B₋₋ Database records should always trump or win over B₋₋ database records. This option is implemented by changing the CIG type to 112--the processing during unloading the records changes the record value in the A₋₋ Database to match the current record value in the B₋₋ Database.

The user may choose to be notified in case of any conflict. The user is notified via a dialog box 30, shown in FIG. 20, whenever a CIG type conflict of 102 or 213 arises. The dialog box shows the record that is involved in the conflict 31. It also shows the A₋₋ Database 32 and B₋₋ Database 33 values for all conflicting fields, in a tabular display, with Field Names appearing in the left column 34. A dropdown list (not shown) in the lower left hand corner of the dialog 37, offers a total of three choices--add, ignore, and update. The use may choose to add new records or ignore the conflict. The user may also choose that the A₋₋ Record or B₋₋ Record should be used to update the other record. The user may also decide to create a compromise record by choosing values of different fields and then choosing update option. In this case, the CIG type is changed to 132, which results in an updating both databases with the new record compromise record.

When the user has chosen to be notified in case of conflict, if the user chooses to ignore conflict or that either the record of the A₋₋ Database or the B₋₋ DATABASE should win, the CIG type is left as a conflict CIG type (102 or 213) and a separate Conflict Resolution Choice is stored in the FLAGS word associated with each CIG member.

The final step in setting CIG₋₋ Types is the process for dealing with difficulties which arise from exclusion lists. For example, in a triple Recurring Master CIG, suppose the History File Recurring Master does not have any excluded instances. The A₋₋ Record has the following exclusion list:

12/1/96, 12/8/96 The B₋₋ Record has the following exclusion list:

1/1/97, 1/8/97, 1/15/97, 1/22/97, 1/29/97

If comparison of the Recurring Masters includes comparing exclusion list Field Values, this set of changes would cause the Synchronizer to report a CIG type 213 conflict.

If the Conflict Resolution Option is set to A₋₋ Database record wins, then the outcome prescribed by the Synchronizer would be for the A₋₋ Database to keep its exclusion list as is and for the B₋₋ Database to make its exclusion list match that of the A₋₋ Database.

The result would be to have a lot of duplicate entries in both Databases. The A₋₋ Database would have five duplicate entries in January 97--that is the five unmodified Recurring Master instances, plus the five modified instances added across from B₋₋ Database to A₋₋ Database. The B₋₋ Database would have five duplicate entries in January 97, since synchronization has wiped out the five exclusions that were previously recorded in the B₋₋ Database exclusion list.

Two steps are implemented for dealing with this problem. First, the COMPARE function does not take into account exclusion list differences when comparing recurring records. Second, referring to FIG. 21, any new exclusions added on to one recurring record will be added to the other record. The merging of exclusion lists is done regardless of any updates or conflicts, even unresolved conflicts, between the A₋₋ Database and B₋₋ Database copies of a Recurring Master. One exception is for CIG type 102 conflict which is left unresolved where Exclusion lists are not merged, because the user has chosen to leave those records as they are.

In most cases where it is necessary to merge exclusion lists, the CIG types and/or the Conflict Resolution Choice to arrange for all necessary updates to be performed during the unloading phases of synchronization.

First, A₋₋ Database and B₋₋ Database records' exclusion lists are compared. In case of databases which do not permit recurring items, the exclusion list of the Synthetic Master is compared to the recurring record of the other database (step 852). If there is no difference, then nothing is done (step 853). If there are differences, then it is determined which exclusions appear only in one record. This comparison always yields one of the following scenarios: (1) all one-side-only Exclusions are on the A₋₋ Database (so Exclusions should be added to the B₋₋ Database); (2) all one-side-only Exclusions are on the B₋₋ Database (so Exclusions should be added to the A₋₋ Database); and (3) there are one-side-only Exclusions on both sides (so Exclusions should be added to both databases).

In each of these cases a separate table is used to look up instructions, for how to handle each specific situation (FIGS. 22-24). The tables cover all possible combinations of previous CIG types and outcome codes with all possible exclusion list changes (new and different exclusions added on A₋₋ Database, or on B₋₋ Database, or on both sides). FIG. 22 table is used in case of scenario 1. FIG. 23 table is used in case of scenario 2. FIG. 24 table is used in case of scenario 3 (FIG. 21 steps 854-856).

The analysis of records is now complete, and the records can be unloaded into their respective databases, including any additions, updates, or deletions. However, prior to doing so, the user is asked to confirm proceeding with unloading (FIG. 3, step 108-109). Up to this point, neither of the databases nor the History File have been modified. The user may obtain through the Translation Engine's User Interface various information regarding what will transpire upon unloading.

If the user chooses to proceed with synchronization and to unload, the records are then unloaded in order into the B₋₋ Database, the A₋₋ Database and the History File. The Unloader modules 6,10 of the Translators 5,9 perform the unloading for the databases. The Synchronizer creates the History File and unloads the records into it. The Control Module 2 of the Translation Engine 1 first instructs the B₋₋ Translator to unload the records from Workspace into the B₋₋ Database. Referring to FIG. 25, for each CIG to be unloaded (determined in steps 902-907), based on the CIG₋₋ TYPE and which database it is unloading into (i.e., A or B), the unloader looks up in the table in FIG. 26 the outcome that must be achieved by unloading--that is, whether to update, delete, add, or skip (Leave₋₋ Alone) (step 908). In steps 909-913, the unloader enforces date range restriction for a database subject to date range. The user may select, or a selection may be made by default, whether to enforce the date range sternly or leniently. In case of stern enforcement, all records outside of the current date range would be deleted. This is useful for computers with small storage capacity. In case of lenient enforcement, the records are left untouched.

Based on the result obtained from looking up the unloading outcome in the table, the unloader then either adds a new record (steps 920-926), deletes an existing record (steps 914-919), or updates an existing record (steps 927-933). It should be noted that because we only update those fields which need to be updated (step 928), the fields which were sanitized but need not be updated are not unloaded. Therefore, the values in those fields remain in unsanitized form in the database.

Referring to step 914, in some Applications when a Recurring Master must be added or updated, the record may have to be fanned out despite the ability of the Application to support recurring records. For example, the Schedule+ Translator is generally able to put almost any Recurring Master Item into Schedule+ without fanning, but there are some exceptions. The Schedule+ Translator uses one Schedule section to handle all appointments and events. For appointments, almost any recurrence pattern is allowed, but for events the only allowable true repeat type is YEARLY. DAILY recurring events can be dealt with by being translated into Schedule+ multi-day events which are not recurring but extend over several days by setting the EndDate some time after the Start Date. But for the DAILY case there are restrictions. In particular exclusions in the midst of a multi-day Schedule+ event cannot be created. So the Translator decides that if section type is ToDos or the item is a non-Event Appointment, then the record need not be fanned out. But if item is a YEARLY or DAILY with no exclusions then it can be stored as a Schedule+ yearly or daily event. Otherwise, it must be fanned.

Referring to FIG. 27, steps 950-984 set out the preferred embodiment of fanning recurring records that must be updated. All cases fall within three scenarios, shown in FIG. 29.

In the first scenario a record which is a Recurring Master, and its counterpart in the other database is a Recurring Master, must be fanned now for its own database (steps 951-959). If the CIG₋₋ TYPE of the record is 132 (i.e. update both records), then it is changed to 13F which is a special value specifically for this situation (step 951). For other CIG₋₋ Types, the CIG is broken into three singleton and given CIG₋₋ Types signifying their singleton status. In both of these cases, the function Fanning₋₋ For₋₋ Add (steps 986-996, described below) is called.

In the second scenario, the record was fanned previously and is going to be fanned now also. First, the dates of the instances are recorded in a temporary date array (steps 961-963). This array is compared to an array of the fanned instances of the recurrence pattern of the CIG Recurring Master from the other database (steps 965-966). The dates which are not in the array of fanned instance are marked for deletion (step 967). The dates which are not in the temporary date array should be added to the unloading databases and therefore new FIG records are created for those dates (steps 968-973). The dates which appear in both arrays are compared to the Synthetic Master and marked accordingly for UPDATE or Leave₋₋ Alone (steps 974-978).

In the third scenario, the record which was previously fanned should now be fanned also. The opposing database's record in this scenario is also fanned instances. This is perhaps the most peculiar of the three cases. For example, a database may be able to handle multi-day (i.e. daily recurring) records but not any exclusion dates for such items. Such database may be synchronized with another database which fans all records in the following manner. A record representing a 7-day vacation in the Planner section of the database is fanned out to form 7 individual vacation days in the other database. One instance is deleted in the other database. Upon synchronizing the two databases, b/c the first databases does not does not provide for exclusion lists, the record must now be fanned.

In this scenario, Master Records in a CIG are marked as Garbage. Any FIG members attached to the H₋₋ Record, if any, are also marked as Garbage. All Instances found in the opposing database's FIG are truned to singleton CIGs with CIG type 100 or 001 so that they will be added to the unloader's database when unloading is done. In this way the instances from one database is copied to the database providing for recurring records.

Steps 985-995 describe the Fanning₋₋ For₋₋ Add Function which is used when outcome is to update or when the function is called by the Translator fanning for update. For each instance generated by fanning out the recurring record, a clone of the Recurring Master is created but excluding Rep₋₋ Basic and Rep₋₋ Excl field values and the unique ID field. All adjustable Date Fields (e.g. Start Date, End Date, and Alarm Date) are set and hash values for the new record is computed. The new record is then marked as Fanned₋₋ For₋₋ A or Fanned₋₋ For₋₋ B, as the case may be. This is then attached to the Recurring Master Item as a FIG member.

Following unloading of the B₋₋ RECORDS, the Control Module 2 instructs the A₋₋ Translator to unload the A₋₋ Records from the Workspace (FIG. 3, step 111). This unloading is done in the same way as it was done by the B₋₋ Translator. In case of Rebuild₋₋ All Translators which have to reconstruct the database, all records which were loaded from the database but were not used in synchronization are appended and unloaded as the Translator builds a new database for its Application.

The Control Module 3 next instructs the Synchronizer to create a new History File (step 112). Referring to FIG. 28, for every CIG in the Workspace, it is first determined which record should be unloaded to History File (steps 1001-1003). In the next step, Excl₋₋ Only flag is checked, which is set by the Merge₋₋ Exclusion₋₋ List logic (FIGS. 21-24). If that flag is set, a new record for unloading is created which has all fields taken from the History File record, except that the newly merged exclusion list is inserted into that record (step 1004). Before storing the record in the History File, all Flag Bits in the Extended Index are cleared except the bit that indicating whether or not this is a recurring item (step 1005). The item is marked as a History File record to indicate its source. The CIG, FIG, and SKG are reset. All the HASH values and Start&EndDate&Time will be stored. All applicable unique ID are also stored (Steps 1006-1009). The current record is then stored in the new History File (step 1010). If the current record is a Recurring Master for an ID-bearing FIG, we now store the whole FIG (i.e. all Fanned Instances) in the History File, with the FIG linkage words set in the History File to hold the FIG records together (step 1011). Fanned instances which do not bear unique IDs are not stored in the History File since they can be re-generated by merely fanning out the Recurring Master.

Once all records are unloaded, various information necessary for identifying this History File and for the next synchronization are written into the History File (step 1013).

At this point Synchronization is complete.

Applications, such as scheduling Applications, often have more than one database. Each of these databases are known as sections. Each of these sections contain different data and must be synchronized with their corresponding sections in other Applications. However, there is not necessarily a one to one relationship between sections of various Applications. For example, Application A may comprise of the following sections: Appointments, Holidays, Business Addresses, Personal Addresses, and ToDo. Application B however may comprise of the following sections: Appointments, Addresses, ToDo-Tasks, and ToDo-Calls. Although the general character of the sections are the same, there is not a one to one relation between the sections of these two Applications: Appointments and Holidays in A contain the same type of data as Appointments in B; Business Addresses and Personal Addresses in A contain the same type of data as Addresses in B; and ToDo in A contains the same type of data as ToDo-Tasks and ToDo-Calls in B. Therefore, when synchronizing the sections of these two Applications, it is necessary to synchronize at least two sections of one Application with one section of another Application.

The preferred embodiment performs this type of synchronization by providing for a number of section categories: Appointment, ToDo, Note, Address, and General Database. All sections of a particular Application are studied and categorized according to this categorization. Therefore, in the above example of Application A, Appointments and Holidays are categorized Appointment type sections (or database), Business Address and Personal Address as Address type sections, and ToDo as a ToDo type section.

For creating the map for mapping sections onto each other, an exact section match is always sought between sections of the two Applications. If not, one of the sections which were categorized as a section type is chosen to be the Main₋₋ Section among them. Other sections of the same type are referred to as subsections. All databases of the same type from the other Application will be mapped onto the Main₋₋ Section.

To properly synchronize from one time to the next, it is necessary to keep track of the source of records in the Main₋₋ Section. In the preferred embodiment, if a record in the Main₋₋ Section of the A₋₋ Application does not come from the Main₋₋ Section of the B₋₋ Application, one of fields in the record, preferably a text field, is tagged with a unique code identifying the subsection which is the source of the record. This is the record's Origin Tag. All records in the Workspace and the History File include a hidden internal field called ₋₋ subType which contains the unique subsection code. Main₋₋ Section's field value in the preferred embodiment is zero so that it will not be tagged. When a record is loaded from a database into the Synchronization Workspace, the tag is stripped from the TagBearer field and put in the ₋₋ subType field. If there is no tag, then the ₋₋ subType is set to be the subType of the present section. If the TagBearer field is mapped then when reading records into the Workspace the tag, if any, is stripped from the TagBearer field value place it in ₋₋ subtype.

Conversely when unloading records from the Workspace to a Database, the TagBearer field is tagged by a tag being added if the record is not from the Main₋₋ Section.

A Fast Synchronization database is a database which provides a method of keeping track of changes, deletions, and additions to its records from one synchronization to the next. These databases speed up the synchronization process because only those records which have been modified need to be loaded from the database. Since the majority of records loaded by regular Translators are unchanged records, far fewer records are loaded from the database into the Synchronizer.

Certain features are required for a database to be a Fast Synchronization database. The database records must have unique IDs and must have a mechanism for keeping track of which records are added, changed, or deleted from synchronization to synchronization, including a list of deleted records. Unique IDs are required to accurately identify records over a period of time.

There are at least two ways to keep track of additions, changes, and deletions in a database.

First, some databases maintain one Dirty bit per record which is a boolean flag that is set when a record is created or modified and is cleared when a function for clearing Dirty bits is called. Some databases offer a Clear DirtyBit function that clears the bit of an individual record. Other databases offer a ClearDirtyBits function that clears the Dirty bits of all records in a database. The record-specific ClearDirtyBit function allows the preferred embodiment to use the database itself to keep track of additions and changes.

The global ClearDirtyBits function forces the preferred embodiment to clear all Dirty bits at the conclusion of every Synchronization. Then as database edits are made by the user in between synchronizations, the affected records are marked as Dirty. When Synchronization is performed again, only the Dirty records are loaded.

Second, some databases maintain a Date&Time stamp of when the record was added or last time the record was modified. A Translator for such a database finds all records which were added or modified since the previous synchronization by searching for Date&Time stamps more recent than the Date&Time of the Last Synchronization.

A Fast Synchronization database must also keep track of deletions. This is done by maintaining a list of deleted records which can be read by a Translator.

A Translator sending Fast Synchronization database records to the Synchronizer provides only records which have been changed, deleted, and added since the previous synchronization. Therefore, unlike a regular database Translator, a Fast Synchronization Translator does not provide the Synchronizer with unchanged records. Moreover, unlike a regular Translator it provides deleted records, which the regular Translators does not.

In order for such databases to be synchronized without resorting to treating them as regular databases, the Synchronizer transforms Fast Synchronization records from the Translator into the equivalent regular database records. These transformed records are then used by the Synchronizer in the synchronization. There are two transformations which are necessary. First, the Synchronizer needs to transform deleted records received from the Fast Synchronization Translator into a regular database deletions. Second, synchronization needs to transform lack of output by the Fast Synchronization Translator into unchanged records.

The invention performs these transformations by using the History File. During the first synchronization, all records in the Fast Synchronization database are loaded into the history file. As changes, additions, and deletions are made to the Fast Synchronization database, during each of the subsequent synchronizations the same change, additions, and deletions are made to the History File. Therefore, the History File at the end of each subsequent synchronization is an exact copy of the Fast Synchronization database.

When a Fast Synchronization Translator supplies no input for a unique ID H₋₋ Record, the Synchronizer finds the corresponding H₋₋ Record in the Workspace and copies it into the Workspace as a record supplied as if it were loaded by the Fast Synchronization translator itself.

Referring to FIG. 30, steps 1050-1051, the Synchronizer first verifies that there is an appropriate History File. Because the Fast Synchronizing process relies heavily on the History File, it is important to ensure that the same history file as the last Synchronization is used. Moreover, the History File is the background against which the transformation of the Translator outputs into regular Translator outputs takes place. The History File keeps a date and time stamp of the last synchronization. Each of the Fast Synchronization database (if able to) and the Fast Synchronization Translator also stores the same date and time stamp. The time and date stamp is used because it is unlikely that another History File will have exactly the same time and date entry, for the same two databases. It also identifies when last the Fast Synchronizer database and the History File contained the same records.

At the start of an incremental synchronization, the Synchronizer and the Fast Synchronization Translator compare date and time stamps. If time and date stamp synchronization parameters have changed since the previous synchronization, then the synchronization proceeds from scratch (step 1052). In a synchronization from scratch all records in the Fast Synchronization database are loaded into the History File.

In the preferred embodiment, all records supplied as Fast Synchronization inputs have a special hidden field called ₋₋ Delta, which carries a single-letter value--`D` for Delete or `A` for Add and `C` for Change. Records are loaded by the Fast Synchronization Translator into the Workspace (step 1054). If necessary the records are mapped when loaded. Records which are marked as changes or additions are sanitized by the Translator for the other database, but deleted records are not because their field values are going to be deleted (step 1055). Orientation analysis (FIG. 11) is performed on the records so that all deletions and changes to Fast Synchronization database records are joined with their History File counterparts in unique ID bearing CIGs (step 1107).

All History File records and their CIGs are now examined. If there is no corresponding record from the Fast Synchronization database, it means that the record was unchanged. A clone of the record is made, labelled as being from Fast Synchronization database, and joined to the H₋₋ Record's CIG. At this point the deleted Fast Synchronization database records marked as deletions are removed from CIGs (step 1109). The Fast Synchronization records marked as changed are joined in doubleton CIGS. Those marked as additions are singletons. At this point, the synchronization can proceed as if record of a unique ID bearing regular database were just loaded into the Workspace.

Whenever we are loading from a Fast Synchronization database, all records are loaded so that at the end of synchronization the history file will be the same as the Fast Synchronization Database. Therefore, referring to FIG. 31, in order to perform date range limited synchronization, the invention marks the records which fall outside the current and the previous date ranges. For a record marked as an addition, or during synchronizing from scratch, if the record falls outside the current date range, it is marked as Out₋₋ Of₋₋ Range (steps 1101 and 1153-1154). This record will be written into the History File but not into the other database or take part in the synchronization. When the Fast Synchronization database records are loaded from the History File, if they fall outside of the previous date range, they are marked as Bystander (steps 1152-1157). If a Bystander record forms a CIG with a Fast Synchronization record marked as a deletion or a change, the Bystander is marked with a Garbage flag because its field values serve no useful purpose any more: the record marked as DELETION should be deleted and the record marked as CHANGED should replace the Bystander H₋₋ Record (step 1162).

H₋₋ Records for which there are no inputs are transformed in the same manner as before (steps 1164-1165). If a Bystander record falls within the current date range, it is equivalent to a regular database record coming into the current date range. Therefore, the H₋₋ Record is cloned and marked as a Fast Synchronizer record while the Bystander record is marked as Garbage (steps 1166-1171). Therefore, just like a new record of a regular database, it has no H₋₋ Record counterpart.

If the user selects to abort a synchronization or selects the option to ignore a conflict or conflicts in general, some of the records loaded from the Fast Synchronization database will not be accepted and recorded in the History File. Therefore, the Translator should provide that record again at the next synchronization. However, because Fast Synchronization Translators supply only records which have been changed, deleted, or added since the previous synchronization, the records which were not accepted will not be supplied. Therefore, in the invention, Fast Synchronization Translator waits for an acknowledgement from the Synchronizer that the record has been accepted.

In case no such acknowledgement is received for a record, the Translator needs to be able to provide that record again to the Synchronizer. If the database allows resetting individual Dirty bits, the Translator merely does not set that bit. If not, the Translator keeps a separate file in which it keeps a record of which Fast Synchronization records were not accepted. The file may contain the unique IDs of those records. The Translator then uses that file to provide the synchronizer with those records during the next synchronization.

Other embodiments are within the following claims. 

I claim:
 1. A computer implemented method of synchronizing at least a first and a second database each containing dated records such as events, wherein the records of the first database extend across a narrow date range narrower than the date range of the records of the second database, the method comprising:performing a prior synchronization across a prior date range set using the date of the prior synchronization and the narrow date range; storing the prior date range and a history file containing information representative of the content of the databases following the prior synchronization; performing a current synchronization across a date range that combines the prior date range with a current date range set using the date of the current synchronization and the narrow date range.
 2. The method of claim 1 wherein the date of each record being synchronized is compared to a start and stop date of a date range to determine whether the record is in range.
 3. A computer implemented method of synchronizing at least a first and a second database, each one containing date bearing records, wherein the date comprises a user-specified date, the method comprising:identifying date bearing records of the first and second database that are within a narrow date range narrower than a date range of the records of one of the first and the second databases; and performing a current synchronization across the narrow date range by synchronizing the identified date bearing records.
 4. The method of claim 3 wherein the step of performing a current synchronization further comprises adding, modifying, or deleting records of the first database within the narrow date range.
 5. The method of claim 3 wherein the step of performing a current synchronization further includes deleting records of the first database that are outside of the narrow date range.
 6. The method of claim 3 wherein the narrow date range has a start date and a stop date and the date of a record being synchronized is compared to the start date and the stop date of the narrow date range to determine whether the record is within the narrow date range.
 7. The method of claim 6 wherein the date of a record being synchronized includes a record start date and a record stop date, the method further comprising:performing a comparison of the record start date to the stop date of the narrow date range and of the record stop date to the start date of the narrow date range; determining based on the comparison whether the record is within the narrow date range.
 8. The method of claim 3 wherein the first database contains a recurring record, the method further comprising fanning the recurring record within the narrow date range.
 9. The method of claim 3 wherein the first database contains a recurring record, further comprising:fanning the recurring record within a useful portion of the narrow date range, the useful portion being determined by application of a preference based on a current date of the current synchronization.
 10. The method of claim 9 wherein the preference includes a preference for future dates compared to the current date over past dates compared to the current date.
 11. The method of claim 9 wherein the preference includes a preference for dates closer to the current date over dates further from the current date.
 12. The method of claim 3 wherein a prior synchronization was performed across a prior narrow date range, such prior narrow date range being different from a current narrow date range of the current synchronization, wherein records representatives of the records of the first and second databases during the prior synchronization are stored in a history file, and wherein performing the current synchronization further comprises performing the synchronization using the history file and the prior narrow date range.
 13. The method of claim 12 wherein the narrow date range is a concatenation of the current narrow date range and the prior narrow date range stored in a history file during the prior synchronization.
 14. The method of claim 12 wherein the step of performing a current synchronization further comprises adding, modifying, or deleting records of the first database that are within the current narrow date range.
 15. The method of claim 12 wherein the step of performing a current synchronization further includes deleting records of the first database that were present during a previous synchronization and that, following the current synchronization, are outside of the current narrow date range.
 16. The method of claim 12 wherein the step of performing a current synchronization further includes updating or deleting records of the first and second databases that are outside of the current narrow date range and within the narrow date range, based on the current synchronization.
 17. The method of claim 12 wherein the step of performing a current synchronization further comprises, based on a selection by a user, performing one of:(a) deleting the records of the first database that were present during a previous synchronization and that, following the current synchronization, are outside of the current narrow date range, and (b) updating or deleting records of the first and second databases that are outside of the current narrow date range and within the narrow date range, based on the current synchronization.
 18. The method of claim 12 wherein one of the narrow date range, the prior narrow date range, and the current narrow date range includes a start date and a stop date and the date of a record being synchronized is compared to the start date and the stop date to determine whether the record is within a corresponding one of the narrow date range, the prior narrow date range, and the current narrow date range.
 19. The method of claim 18 wherein a record being synchronized includes a record start date and a record stop date, the method further comprising:performing a comparison of the record start date to the stop date of one of the narrow date range, the prior narrow date range, and the current narrow date range, and of the record stop date to the start date of the corresponding one of the narrow date range, the prior narrow date range, and the current narrow date range; and determining based on the comparison whether the record is within the corresponding one of the narrow date range, the prior narrow date range, and the current narrow date range.
 20. The method of claim 12 wherein the current narrow date range comprises a relative narrow date range, the relative narrow date range being determined relative to a date of the current synchronization.
 21. The method of claim 3 wherein the narrow date range comprises a relative narrow date range, the relative narrow date range being determined relative to a date of the current synchronization.
 22. The method of claim 3 wherein the first database contains a first plurality of non-recurring records representing a plurality of recurring date bearing instances, the method further comprising:generating a synthetic recurring record using the first plurality of non-recurring records; performing a synchronization of the synthetic recurring record with a record of the second database; if one of the record, the synthetic record, and a non-recurring record in the first plurality of non-recurring records is outside the narrow date range, fanning the synthetic record, or the record of the second database if it is a recurring record, into a second plurality of non-recurring records within the narrow date range.
 23. The method of claim 3 wherein the narrow date range comprises a concatenation of a first date range for the first database and a second date range for the second database.
 24. The method of claim 3 wherein records representatives of the records of the first and second databases during the prior synchronization are stored in a history file, and wherein performing the current synchronization includes performing the synchronization using the history file.
 25. The method of claim 3 wherein the user-specified date includes a date determined based on a user-specified criterion.
 26. The method of claim 25 wherein the date determined based on the user-specified criterion includes a date of an instance of a recurring record.
 27. The method of claim 3 further comprising obtaining from a user information to determine the narrow date range.
 28. A computer implemented method of synchronizing at least a first and a second database, each one containing date bearing records, wherein the date comprises a user-specified date, the method comprising:identifying date bearing records of the first database that are within a narrow date range narrower than a date range of the records of the first database; and synchronizing at least one of the identified date bearing records of the first database with one of the date bearing records of the second database.
 29. The method of claim 28 wherein the step of performing a current synchronization further includes deleting records of the first database that are outside of the narrow date range.
 30. The method of claim 28 wherein the first database contains a recurring record, the method further comprising fanning the recurring record within the narrow date range.
 31. The method of claim 28 wherein the first database contains a recurring record, further comprising:fanning the recurring record within a useful portion of the narrow date range, the useful portion being determined by application of a preference based on a current date of the current synchronization.
 32. The method of claim 28 wherein records representatives of the records of the first and second databases during a prior synchronization are stored in a history file, and wherein performing the current synchronization includes performing the synchronization using the history file.
 33. The method of claim 32 wherein the prior synchronization was performed across a prior narrow date range, such prior narrow date range being different from a current narrow date range of the current synchronization, and wherein performing the current synchronization further comprises performing the synchronization using the history file and the prior narrow date range.
 34. The method of claim 33 wherein the narrow date range is a concatenation of the current narrow date range and the prior narrow date range stored in a history file during the prior synchronization.
 35. The method of claim 33 wherein the step of performing a current synchronization further includes deleting records of the first database that were present during a previous synchronization and that, following the current synchronization, are outside of the current narrow date range.
 36. The method of claim 33 wherein the step of performing a current synchronization further includes updating or deleting records of the first and second databases that are outside of the current narrow date range and within the narrow date range, based on the current synchronization.
 37. The method of claim 28 wherein the current narrow date range comprises a relative narrow date range, the relative narrow date range being determined relative to a date of the current synchronization.
 38. The method of claim 28 further comprising obtaining from a user information to determine the narrow date range.
 39. The method of claim 28 wherein the user-specified date includes a date determined based on a user-specified criterion.
 40. The method of claim 39 wherein the date determined based on the user-specified criterion includes a date of an instance of a recurring record.
 41. A computer program, resident on a computer readable medium, for synchronizing at least a first and a second database each containing dated records such as events, wherein the records of the first database extend across a narrow date range narrower than the date range of the records of the second database, comprising instructions for:performing a prior synchronization across a prior date range set using the date of the prior synchronization and the narrow date range; storing the prior date range and a history file containing information representative of the content of the databases following the prior synchronization; performing a current synchronization across a date range that combines the prior date range with a current date range set using the date of the current synchronization and the narrow date range.
 42. The computer program of claim 41 wherein the date of each record being synchronized is compared to a start and stop date of a date range to determine whether the record is in range.
 43. A computer program, resident on a computer readable medium, for synchronizing at least a first and a second database, each one containing date bearing records, wherein the date comprises a user-specified date, comprising instructions for:identifying date bearing records of the first and second database that are within a narrow date range narrower than a date range of the records of one of the first and the second databases; and performing a current synchronization across the narrow date range by synchronizing the identified date bearing records.
 44. The computer program of claim 43 wherein the instruction for performing a current synchronization further comprises instructions for adding, modifying, or deleting records of the first database within the narrow date range.
 45. The computer program of claim 43 wherein the instruction for performing a current synchronization further includes instructions for deleting records of the first database that are outside of the narrow date range.
 46. The computer program of claim 43 wherein the narrow date range has a start date and a stop date and the date of a record being synchronized is compared to the start date and the stop date of the narrow date range to determine whether the record is within the narrow date range.
 47. The computer program of claim 46 wherein the date of a record being synchronized includes a record start date and a record stop date, the computer program further comprises instructions for:performing a comparison of the record start date to the stop date of the narrow date range and of the record stop date to the start date of the narrow date range; determining based on the comparison whether the record is within the narrow date range.
 48. The computer program of claim 43 wherein the first database contains a recurring record, the computer program further comprising instructions for fanning the recurring record within the narrow date range.
 49. The computer program of claim 43 wherein the first database contains a recurring record, further comprising instructions for:fanning the recurring record within a useful portion of the narrow date range, the useful portion being determined by application of a preference based on a current date of the current synchronization.
 50. The computer program of claim 49 wherein the preference includes a preference for future dates compared to the current date over past dates compared to the current date.
 51. The computer program of claim 49 wherein the preference includes a preference for dates closer to the current date over dates further from the current date.
 52. The computer program of claim 43 wherein a prior synchronization was performed across a prior narrow date range, such prior narrow date range being different from a current narrow date range of the current synchronization, wherein records representatives of the records of the first and second databases during the prior synchronization are stored in a history file, and wherein performing the current synchronization further comprises instructions for performing the synchronization using the history file and the prior narrow date range.
 53. The computer program of claim 52 wherein the narrow date range is a concatenation of the current narrow date range and the prior narrow date range stored in a history file during the prior synchronization.
 54. The computer program of claim 52 wherein the instruction for performing a current synchronization further comprises instructions for adding, modifying, or deleting records of the first database that are within the current narrow date range.
 55. The computer program of claim 52 wherein the instruction for performing a current synchronization further includes instructions for deleting records of the first database that were present during a previous synchronization and that, following the current synchronization, are outside of the current narrow date range.
 56. The computer program of claim 52 wherein the instruction for performing a current synchronization further includes instructions for updating or deleting records of the first and second databases that are outside of the current narrow date range and within the narrow date range, based on the current synchronization.
 57. The computer program of claim 52 wherein the instruction for performing a current synchronization further comprises instructions for, based on a selection by a user, performing one of:(a) deleting the records of the first database that were present during a previous synchronization and that, following the current synchronization, are outside of the current narrow date range, and (b) updating or deleting records of the first and second databases that are outside of the current narrow date range and within the narrow date range, based on the current synchronization.
 58. The computer program of claim 52 wherein one of the narrow date range, the prior narrow date range, and the current narrow date range includes a start date and a stop date and the date of a record being synchronized is compared to the start date and the stop date to determine whether the record is within a corresponding one of the narrow date range, the prior narrow date range, and the current narrow date range.
 59. The computer program of claim 58 wherein a record being synchronized includes a record start date and a record stop date, the computer program further comprising instructions for:performing a comparison of the record start date to the stop date of one of the narrow date range, the prior narrow date range, and the current narrow date range, and of the record stop date to the start date of the corresponding one of the narrow date range, the prior narrow date range, and the current narrow date range; determining based on the comparison whether the record is within the corresponding one of the narrow date range, the prior narrow date range, and the current narrow date range.
 60. The computer program of claim 52 wherein the current narrow date range comprises a relative narrow date range, the relative narrow date range being determined relative to a date of the current synchronization.
 61. The computer program of claim 43 wherein the narrow date range comprises a relative narrow date range, the relative narrow date range being determined relative to a date of the current synchronization.
 62. The computer program of claim 43 wherein the first database contains a first plurality of non-recurring records representing a plurality of recurring date bearing instances, the computer program further comprising instructions for:generating a synthetic recurring record using the first plurality of non-recurring records; performing a synchronization of the synthetic recurring record with a record of the second database; if one of the record, the synthetic record, and a non-recurring record in the first plurality of non-recurring records is outside the narrow date range, fanning the synthetic record, or the record of the second database if it is a recurring record, into a second plurality of non-recurring records within the narrow date range.
 63. The computer program of claim 43 wherein the narrow date range comprises a concatenation of a first date range for the first database and a second date range for the second database.
 64. The computer program of claim 43 wherein records representatives of the records of the first and second databases during the prior synchronization are stored in a history file, and wherein the performing the current synchronization includes instructions for performing the synchronization using the history file.
 65. The computer program of claim 43 wherein the user-specified date includes a date determined based on a user-specified criterion.
 66. The computer program of claim 65 wherein the date determined based on the user-specified criterion includes a date of an instance of a recurring record.
 67. The computer program of claim 43 further comprising instructions for obtaining from a user information to determine the narrow date range.
 68. A computer program, resident on a computer readable medium, for synchronizing at least a first and a second database, each one containing date bearing records, wherein the date comprises a user-specified date, comprising instructions for:identifying date bearing records of the first database that are within a narrow date range narrower than a date range of the records of the first database; and synchronizing at least one of the identified date bearing records of the first database with one of the date bearing records of the second database.
 69. The computer program of claim 68 wherein the instruction for performing a current synchronization further includes instructions for deleting records of the first database that are outside of the narrow date range.
 70. The computer program of claim 68 wherein the first database contains a recurring record, the computer program further comprising instructions for fanning the recurring record within the narrow date range.
 71. The computer program of claim 68 wherein the first database contains a recurring record, further comprising instructions for:fanning the recurring record within a useful portion of the narrow date range, the useful portion being determined by application of a preference based on a current date of the current synchronization.
 72. The computer program of claim 68 wherein records representatives of the records of the first and second databases during the prior synchronization are stored in a history file, and wherein the performing the current synchronization includes instructions for performing the synchronization using the history file.
 73. The computer program of claim 72 wherein the prior synchronization was performed across a prior narrow date range, such prior narrow date range being different from a current narrow date range of the current synchronization, and wherein performing the current synchronization further comprises instructions for performing the synchronization using the history file and the prior narrow date range.
 74. The computer program of claim 73 wherein the narrow date range is a concatenation of the current narrow date range and the prior narrow date range stored in a history file during the prior synchronization.
 75. The computer program of claim 73 wherein the instruction for performing a current synchronization further includes instructions for deleting records of the first database that were present during a previous synchronization and that, following the current synchronization, are outside of the current narrow date range.
 76. The computer program of claim 73 wherein the instruction for performing a current synchronization further includes instructions for updating or deleting records of the first and second databases that are outside of the current narrow date range and within the narrow date range, based on the current synchronization.
 77. The computer program of claim 68 wherein the narrow date range comprises a relative narrow date range, the relative narrow date range being determined relative to a date of the current synchronization.
 78. The computer program of claim 68 further comprising instructions for obtaining from a user information to determine the narrow date range.
 79. The computer program of claim 68 wherein the user-specified date includes a date determined based on a user-specified criterion.
 80. The computer program of claim 77 wherein the date determined based on the user-specified criterion includes a date of an instance of a recurring record. 